Alaska is a land of countless lakes, many of them impressively large. The largest of all is Lake Iliamna, which Ivan Sanderson described as "not a lake at all but really an inland sea." Some 80 miles long and with a surface area over a thousand square miles, Iliamna is approximately the size of the state of Connecticut. This makes it the second-largest fresh-water lake (after Lake Michigan) lying entirely within the United States. Iliamna has a mean depth of 144 feet and is over 900 feet deep in some areas. The lake is connected to Bristol Bay, 60 miles southwest, by the Kvichak River, through which such marine mammals as harbor seals and belugas can travel. Iliamna even has a resident population of harbor seals, along with a very successful sport-fishing industry.

The most intriguing thing about Lake Iliamna, however, is the possibility it houses huge unknown animals. These are totally unlike the oft-reported "lake monsters," with their small heads and long necks. Instead, the animals alleged to live in Iliamna look like gigantic fish.

Reports of something odd in Iliamna go back to the Aleut and other indigenous tribes, although no one knows how far back in time these stories began. The Aleuts did not hunt the lake's creatures, and believed them to be dangerous to men fishing in small boats. Some early white settlers and visitors reportedly saw the things, too, but the stories about Iliamna did not gain wide circulation until the 1940s, when pilots began spotting monsters from the air. The flyers' descriptions generally matched the native tales. The lake's mystery inhabitants were most often described as long, relatively slender animals, like fish or whales, up to 30 feet in length.

In 1988, bush pilot and fishing guide "Babe" Alsworth (commonly misspelled Aylesworth) recounted his 1942 sighting in an interview with Cryptozoologist Loren Coleman. Alsworth saw several animals, each well over 10 feet long, in a shallow part of the lake. He said they had fishlike tails and elongated bodies. He described the color as "dull aluminum." Larry Rost, a survey pilot for the U.S. government, saw a lone creature of the same type while crossing the lake at low altitude in 1945. Rost thought the animal was over 20 feet long.

There have been at least three attempts to find or catch Iliamna's mystery inhabitants. In the 1950s, sportsman Gil Paust and three companions (one a fisherman named Bill Hammersly, who had been in the plane with Alsworth in 1942 and shared his amazing sighting), tried to fish for the creatures. According to Paust, something grabbed the moose meat used as bait and snapped the steel cable it was hooked to. In 1959, oilman and Cryptozoology enthusiast Tom Slick hired Alsworth to conduct an aerial search of the lake, but nothing was sighted. An expedition in 1966 also apparently met with no success, as no results were announced. In 1979, the Anchorage Daily News offered $100,000 for tangible evidence of the Iliamna creatures. The reward brought both serious and non-serious researchers (one man reportedly played classical music to lure the animals up). Apparently, there has never been a well-financed expedition with sophisticated sonar and photographic gear.

According to a 1988 article in Alaska magazine, a noteworthy (but unnamed) witness was a state wildlife biologist. In 1963, this official was reportedly flying over the lake alone when he spotted a creature which appeared to be 25 to 30 feet long. In the ten minutes it was under observation, the thing never came up for air. Other flying witnesses mentioned in media accounts include a geologist who flew over the lake with two companions in 1960, reportedly spotting four 10-foot fish, and air taxi pilot Tim LaPorte in 1977. In LaPorte's case, the veteran pilot and air-service owner was near Pedro Bay, at the northeast end of the lake. He was flying just a few hundred feet above a flat calm surface. LaPorte and his two passengers, one a visiting Michigan fish and game official, saw an animal lying still, its back just breaking the surface. As the plane came closer, the creature made a "big arching splash" and dove straight down. LaPorte remembers watching a large vertical tail moving as the animal sounded. Comparing the object to an 18-foot boat often observed from the same altitude, LaPorte and his companions estimated the thing was 12 to 14 feet long. LaPorte described the object as either dark gray or dark brown. LaPorte had been a passenger in a different aircraft in 1968 when the other two individuals in the plane had a very similar sighting. (LaPorte, who was in the left seat, could not see the animal from his side.)

Modern sightings have occurred mostly near the villages of Iliamna and Pedro Bay. It was off the latter town in 1988 that several witnesses, three in a boat and others on shore, reported one of the creatures. In this case, it was described as black. One witness thought she could see a fin on the back, with a white stripe along it.

Lake Iliamna is still an isolated body of water, its shores largely unpopulated. The largest village, Kakhonak, counts only 200 permanent residents. The lake cannot be reached overland. Summer visitors must come by boat or fly in to a single airstrip. If there are unusual creatures in the lake, it's hardly surprising that a long time can pass between good sightings.

A common theory about the Lake Iliamna creatures (sometimes called "Illies") is that they are gigantic sturgeon. These could be either an outsized population of a known type or an unknown species. Sturgeon - huge fish with armorlike scutes covering their backs and a heritage going back before the dinosaurs - match most descriptions from Iliamna fairly well. A witness named Louise Wassillie, who watched a creature from her fishing boat in 1989, said specifically, "It's only a fish. It was about 20 feet long and had a long snout. Probably a sturgeon." Biologist Pat Poe of the Fisheries Research Institute (FRI) at the University of Washington, who has studied the salmon populations in Iliamna and neighboring Lake Clark, once commented, "I'm sure there's a big fish. I think the lakes have a lot of interesting secrets. We don't know much about other resident fish in the lake." Warner Lew, currently the senior biologist with the FRI's Alaska Salmon Program, agrees the lake seems a suitable habitat for large sturgeon. Lew reports several witnesses have told him of sighting giant fish, but he has yet to see any fish larger than a four-foot Northern pike in his 24 years of research visits to the lake. The white sturgeon (Acipenser transmontanus) is the largest known fresh-water fish in North America. The record claim for a white sturgeon, caught in Canada's Fraser River in 1912, was 20 feet in length and 1,800 pounds. A fish of 1,500 pounds was reported caught in 1928 in the Snake River in the northwestern United States. An 11-foot specimen weighing 900 pounds was found dead on the shore of Seattle's Lake Washington in 1987. Sturgeon expert Don Larson, curator of the Sturgeon Page Website, reports that sturgeons over 10 feet long are often caught in the Fraser and Columbia Rivers. Larson comments, "Most biologists I've talked to say that white sturgeon over 20 feet and 1800 pounds is highly probable." White sturgeons are not known from Iliamna, but have been found in other Alaskan lakes and in coastal waters as far north as Cook Inlet. There is a single record of a catch in Bristol Bay, which puts a migration to Iliamna within the bounds of possibility. It's also plausible that white sturgeon became trapped in the lake thousands of years ago, when the last glaciers receded, and have developed in isolation. Sturgeons are bottom-feeders and would rarely be seen near the surface, which fits the Iliamna phenomenon. The appearance of white sturgeon - gray to gray-brown in color, with huge heads and long cylindrical bodies -match most Iliamna reports. (No one is certain how the species got the name "white sturgeon," although some genuinely white specimens have been reported from salt water.) It may be a distinct sturgeon population has developed, distinguished from the known white sturgeon mainly by unusual size. Whether this hypothetical type is different enough to be a new species is unknown. There is plenty of food in Iliamna, where averages of 20 million sockeye salmon return to the lake from the sea every year. There is also plenty of room. Iliamna has 15 times the volume of Loch Ness. At the same time, it must be admitted there is no physical or film evidence for unknown creatures of any kind. A landlocked population of fish becoming larger than their relatives which are anadromous (dividing their lives between fresh and salt water) would be unusual. In most cases where a species has become split between freshwater and anadromous populations, as with salmon, the freshwater variety becomes smaller. However, this rule may not be valid for Lake Iliamna, with its huge size and bountiful food supply.

So what is lurking in Lake Iliamna? Sturgeons? Monsters? Tall tales? Or something completely different? Whatever is going on constitutes one of the most intriguing lake monster mysteries in the world. If I had to pick one "monster" lake to bet on as the home of a real creature of prodigious size, it is Iliamna, rather than the better-known candidates in Canada and Scotland, where I would put my money.